Find Patents Worldwide

World Intellectual Property Organization: search WIPO patents with key 
words in English, German or French.
http://www.wipo.int/ipdl/en/

European Patent Office (Recherche avancée): search EP patents with key 
words in English, German or French.
http://fr.espacenet.com/advancedSearch?locale=fr_FR

PatentLens.Net: search patents with key words in English, German or 
French (EP, WO, AU).
http://www.patentlens.net/patentlens/structured.cgi

Canadian Patent Office: Search patents (worldwide) with key words in 
English or French:
http://patents.ic.gc.ca/cipo/cpd/en/search/advanced.html